Conventional hair dryers generally have a fan which sucks air from the exterior through an air intake, and then blows it past one or more electrical heating elements where the blown air is heated. The heated air continues along its path within the hair dryer to a relatively large orifice through which the heated air is blown to the exterior of the dryer, usually onto the hair adjacent to which the dryer is being held. The dryer is moved along the hair to achieve drying of the entire hair.
Drying is accomplished solely by way of convection which comprises the blowing of the hot air onto the hair. It is well known to increase the rate of convection by applying a constrictor over the blowing orifice thereby to increase the pressure of the blown air and thus the velocity of the blown hot air, thereby to intensify drying and increase penetration of the hot air throughout the hair.
An aim of hair dryer design has been to increase the drying rate of hair. This has been achieved by increasing the volume of air delivered by the blowers such as by changing the design of the fan or by accelerating its rotation. Increasing the fan performance is often combined with increasing the size and voltage of the heating coils to transfer more heat to the air blown past the heating coils and out through the drying orifice. In the wattage race in hair dryer design, the provision for 1,200 watt/hour power has become commonplace.
In the usual form of prior art hair dryers the heater or heaters are surrounded by a tubular or annular shroud, the air is blown through that tubular shroud past the heaters and, except for any added constrictor elements, the end of the tubular shroud is usually open and comprises the large orifice through which the heated air is blown.
These aforementioned design changes have increased drying capacity to a finite limit to preserve the hand held character of the hair dryer. Therefore, there is a need in the field of hair dryer design yet further to increase the drying capacity of hair dryers without increasing their wattage requirements and maintaining weight and ease of use for continued ability to use a dryer in a hand held manner.